Heart valve diseases are some of most commonly diagnosed cardiac diseases in China, and most of them are found to be heart valve damage caused by rheumatic fever. In recent years, the continually aging population has driven an increasing incidence of valvular degeneration (including calcification, mucoid degeneration, etc.) and valvular damage caused by metabolic disorders.
Conventionally, heart valve replacement surgery is an open-heart procedure conducted under general anesthesia, during which, following an incision made along the patient's sternum (sternotomy), the heart is stopped and blood flow is guided through a “heart-lung” bypass machine (extracorporeal circulation machine). Traditional open surgery brings to the patient significant trauma as well as possible transient disturbances caused by emboli and other issues associated with the use of the heart-lung machine. Complete recovery from the trauma typically costs a couple of months. For some special population groups such as elders, the trauma is particularly unendurable and the recovery needs more time and is sometime even impossible.
Minimally invasive interventional surgery offers a variety of advantages, including needlessness of sternotomy, minimal patient trauma and quick recovery. In the recent ten years, interventional therapies have shown a tendency to be able to cope with not only all diseases curable by traditional medical and surgical treatments but also some diseases that the traditional approaches could not handle. Upon entering the new century, researches on interventional therapies for valvular heart diseases have been experiencing a notable acceleration. Percutaneous valve replacement technologies have evolved from experimental researches to small-scale clinical trials and are likely to have breakthroughs in technical “bottlenecks” to achieve extensive clinical applications. This makes the technologies again a focus of research efforts in the field of interventional cardiology.
Existing systems for delivering cardiac replacement valves are associated with a number of deficiencies. One of the deficiencies is that such systems are typically of high complexity which imposes great requirements on the clinician′ operations and thus causes a high risk of operational mistakes. Another deficiency is that the existing delivery systems are incapable of rapid deployment and retrieve of delivering means after the replacement valve has been corrected located. This leads to an elongated time of their stay within the patient's body and hence increased adverse effects.
Chinese patent document (Patent No. CN2726560Y) describes a device for interventional implantation of a prosthetic heart valve. The device includes a delivery pipe, a locking silk, a pull line, a guide line, a pull line fixing bolt and a locking silk fixing bolt. The rear end of the delivery pipe is provided with at least one pull line branch pipe, each pull line enters the delivery pipe through each pull line branch pipe and extends out from the anterior end of the delivery pipe; each guide silk and each locking silk penetrates the delivery pipe and extends out from the anterior end of the delivery pipe; the pull line fixing bolt can be screwed at the pipe mouth of the pull line branch pipe to fix the pull line, the locking silk fixing bolt can be screwed at the rear end of the delivery pipe to fix the locking silk. While this device can achieve relatively satisfactorily controlled loading and deployment of the replacement prosthetic heart valve, it fails to address the high complexity issue as its operation involves manipulating the pull line and locking silk). Such complicated operation is more likely to cause mistakes and is detrimental to surgery time and quality.
US patent document (Pub. No. US2011/0251683A1) discloses a delivery system which reduces the requirements for the operating clinician and accordingly entails a reduced surgery time. However, in this system, the deployment of the replacement value is done by a significantly inconvenient rotating operation with an allowed angle of each rotation limited to lower than 180 degrees. While this deployment approach is less problematic during the location of the replacement valve, in the rapid deployment phase, it requires the clinician to rotate the control knob at a very high speed, thus leading to increased operational complexity. In addition, the system also suffers from unreliability in its “pushing-pulling” operation since the means for enabling this operation is prone to cause the clinician's finger to slip off during the operation. Finger slippery may lead to an overall movement of the delivery tubular structure which may, in turn, cause dislodgement of the deployed valve stent and thus undesirable conditions such as leakage. Other disadvantages of this conventional system include: inconvenient rotating operation of the functional handle; high risk of operational mistakes of the push-pull button; a single-layered construction of the inner tube assembly that is lack of balance between bending and axial performance.
In summary, the conventional systems have the deficiencies or drawbacks as follows:
1) high complexity that imposes great requirements on the clinician's operations and causes a high risk of operational mistakes;
2) a low operation efficiency because the coupling of the inner tube to a mounting frame provided on a trailing portion of the handle creates inconvenience in operating the rotating means and limits the stroke of each rotation to lower than 180 degrees;
3) incapability of satisfactory rapid deployment after correct location of the replacement valve, either by a pushing-pulling operation because this operation is unreliable as the button can be moved forward or backward only when it is in a pressed-down position, i.e., when being simultaneously driven by two forces from differing directions, which is prone to cause finger slippery and thus dislodgement of the located prosthetic valve, or by a rotating operation because in which the clinician is required to perform the inconvenient and complicated rotation operation at a high speed; and
4) difficulty in valve stent deployment when there occurs a relative rotation between the stent and the tubular structure because the rotation is prone to cause a shear force between a frame of the stent and retention clasps, which will impede the stent from being deployed.
Because of the above described shortcomings of the conventional delivery system, there exists a need for a novel delivery system can be controlled to deliver rapidly, reliably and precisely implantation of the prosthetic heart valve to an expected deployment location by uncomplicated minimally invasive operations.